Bandwith allocation and scheduling in photonic networks

This thesis describes a framework for bandwidth allocation and scheduling in the Agile All-Photonic Network (AAPN). This framework is also applicable to any single-hop communication network with significant signalling delay (such as satellite-TDMA systems). Slot-by-slot scheduling approaches do not provide adequate performance for wide-area networks, so we focus on frame-based scheduling. We propose three novel fixed-length frame scheduling algorithms (Minimum Cost Search, Fair Matching and Minimum Rejection) and a feedback control system for stabilization.MCS is a greedy algorithm, which allocates time-slots sequentially using a cost function. This function is defined such that the time-slots with higher blocking probability are assigned first. MCS does not guarantee 100% throughput, thought it has a low blocking percentage. Our optimum scheduling approach is based on modifying the demand matrix such that the network resources are fully utilized, while the requests are optimally served. The Fair Matching Algorithm (FMA) uses the weighted max-min fairness criterion to achieve a fair share of resources amongst the connections in the network. When rejection is inevitable, FMA selects rejections such that the maximum percentage rejection experienced in the network is minimized. In another approach we formulate the rejection task as an optimization problem and propose the Minimum Rejection Algorithm (MRA), which minimizes total rejection. The minimum rejection problem is a special case of maximum flow problem. Due to the complexity of the algorithms that solve the max-flow problem we propose a heuristic algorithm with lower complexity.Scheduling in wide-area networks must be based on predictions of traffic demand and the resultant errors can lead to instability and unfairness. We design a feedback control system based on Smith's principle, which removes the destabilizing delays from the feedback loop by using a "loop cancelation" technique. The feedback control system we propose reduces the effect of prediction errors, increasing the speed of the response to sudden changes in traffic arrival rates and improving the fairness in the network through equalization of queue-lengths

A dynamically reconfigurable hard-real-time communication protocol for embedded systems

Echtzeitkommunikation ist eine Grundanforderung für viele verteilte eingebettete Systeme. Für eine neue Klasse von Anwendungen sind jedoch nicht nur Echtzeitfähigkeit, sondern auch Flexibilität und Anpassungsfähigkeit notwendige System-Attribute. Um die Flexibilität zu erhöhen, wurde in dieser Arbeit ein neues Kommunikationsprotokoll namens TrailCable konzipiert. Es profitiert von den Eigenschaften des Earliest Deadline First Scheduling-Verfahrens, wie z. B. der optimalen Ausnutzung von Ressourcen und der Unterstützung von heterogenen Tasks. Ein Kommunikationsnetzwerk wird aufgebaut mit Hilfe von voll-Duplex-, Punkt-zu-Punkt-Verbindungen, wobei die Knoten Datenpakete weiterleiten können, um eine Multi-hop Übertragung zu gewährleisten. Es werden Methoden vorgestellt, die es erlauben, automatisch die Kommunikationsanforderungen erfüllende Echtzeit-Kanäle auf das Netzwerk abzubilden. Echtzeit-Kanäle können nur dann aktiviert werden, wenn im Voraus ein Akzeptanztest erfolgreich durchgeführt wurde. Solch eine Prüfung kann mittels eines Tools automatisch erfolgen. Alle dafür notwendigen Netzwerkinformationen werden aus XML-Dateien eingelesen. Zur Laufzeit prüft ein Mechanismus, der Bandbreitenwächter genannt wird, ob die eingelesenen Pakete mit ihrer Spezifikation übereinstimmen, damit Fehler die Echzeitfähigkeit anderer Kanäle nicht beeinträchtigen können. Zeitkritische Funktionen des Kommunikationsprotokolls, wie Scheduling, Bandbreitenwächter, Routing und Uhrsynchronisation, sind mittels dedizierter Hardware implementiert. Ein voll funktionsfähiger FPGA-basierter Prototyp wurde aufgebaut und in zahlreichen Tests evaluiert, um das Echtzeit-Verhalten des Protokolls unter realen Bedingungen zu testen und zu analysieren.Real-time communication is a basic requirement for many distributed embedded systems. However, for an emerging new class of applications not only real-time behavior but also flexibility and adaptability will become necessary system attributes. In order to increase the flexibility of real-time communication systems a new protocol called TrailCable was designed. It takes advantage of the properties of Earliest Deadline First (EDF) scheduling, which include optimal utilization bounds and the possibility to cope with heterogeneous task sets. A communication network is built with full-duplex, point-to-point links, and nodes can route packets to allow multi-hop message delivery. This work introduces methods for automatically mapping real-time channels on a given network directly from communication requirement specifications. The activation of real-time channels in the network is permitted only after a successful schedulability analysis, which can be executed automatically by a tool that checks XML-based network configuration models. At run-time, the characteristics of all incoming packets are checked against their specification by an admission control technique called bandwidth guardian, which is used to ensure that occasional faults will not impair the timeliness of other real-time channels. Time-critical functions of the communication protocol, such as scheduling, admission control, packet routing, and clock synchronization, are implemented by means of dedicated hardware. A fully operational FPGA-based prototype was built and used in different measurement experiments to validate the real-time behavior of the protocol under real conditions.Tag der Verteidigung: 02.04.2012Paderborn, Univ., Diss., 201

Optical flow switched networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 253-279).In the four decades since optical fiber was introduced as a communications medium, optical networking has revolutionized the telecommunications landscape. It has enabled the Internet as we know it today, and is central to the realization of Network-Centric Warfare in the defense world. Sustained exponential growth in communications bandwidth demand, however, is requiring that the nexus of innovation in optical networking continue, in order to ensure cost-effective communications in the future. In this thesis, we present Optical Flow Switching (OFS) as a key enabler of scalable future optical networks. The general idea behind OFS-agile, end-to-end, all-optical connections-is decades old, if not as old as the field of optical networking itself. However, owing to the absence of an application for it, OFS remained an underdeveloped idea-bereft of how it could be implemented, how well it would perform, and how much it would cost relative to other architectures. The contributions of this thesis are in providing partial answers to these three broad questions. With respect to implementation, we address the physical layer design of OFS in the metro-area and access, and develop sensible scheduling algorithms for OFS communication. Our performance study comprises a comparative capacity analysis for the wide-area, as well as an analytical approximation of the throughput-delay tradeoff offered by OFS for inter-MAN communication. Lastly, with regard to the economics of OFS, we employ an approximate capital expenditure model, which enables a throughput-cost comparison of OFS with other prominent candidate architectures. Our conclusions point to the fact that OFS offers significant advantage over other architectures in economic scalability.(cont.) In particular, for sufficiently heavy traffic, OFS handles large transactions at far lower cost than other optical network architectures. In light of the increasing importance of large transactions in both commercial and defense networks, we conclude that OFS may be crucial to the future viability of optical networking.by Guy E. Weichenberg.Ph.D

IP multicast over WDM networks

Ph.DDOCTOR OF PHILOSOPH

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing

Scheduling algorithms for throughput maximization in data networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 215-226).This thesis considers the performance implications of throughput optimal scheduling in physically and computationally constrained data networks. We study optical networks, packet switches, and wireless networks, each of which has an assortment of features and constraints that challenge the design decisions of network architects. In this work, each of these network settings are subsumed under a canonical model and scheduling framework. Tools of queueing analysis are used to evaluate network throughput properties, and demonstrate throughput optimality of scheduling and routing algorithms under stochastic traffic. Techniques of graph theory are used to study network topologies having desirable throughput properties. Combinatorial algorithms are proposed for efficient resource allocation. In the optical network setting, the key enabling technology is wavelength division multiplexing (WDM), which allows each optical fiber link to simultaneously carry a large number of independent data streams at high rate. To take advantage of this high data processing potential, engineers and physicists have developed numerous technologies, including wavelength converters, optical switches, and tunable transceivers.(cont.) While the functionality provided by these devices is of great importance in capitalizing upon the WDM resources, a major challenge exists in determining how to configure these devices to operate efficiently under time-varying data traffic. In the WDM setting, we make two main contributions. First, we develop throughput optimal joint WDM reconfiguration and electronic-layer routing algorithms, based on maxweight scheduling. To mitigate the service disruption associated with WDM reconfiguration, our algorithms make decisions at frame intervals. Second, we develop analytic tools to quantify the maximum throughput achievable in general network settings. Our approach is to characterize several geometric features of the maximum region of arrival rates that can be supported in the network. In the packet switch setting, we observe through numerical simulation the attractive throughput properties of a simple maximal weight scheduler. Subsequently, we consider small switches, and analytically demonstrate the attractive throughput properties achievable using maximal weight scheduling. We demonstrate that such throughput properties may not be sustained in larger switches.(cont.) In the wireless network setting, mesh networking is a promising technology for achieving connectivity in local and metropolitan area networks. Wireless access points and base stations adhering to the IEEE 802.11 wireless networking standard can be bought off the shelf at little cost, and can be configured to access the Internet in minutes. With ubiquitous low-cost Internet access perceived to be of tremendous societal value, such technology is naturally garnering strong interest. Enabling such wireless technology is thus of great importance. An important challenge in enabling mesh networks, and many other wireless network applications, results from the fact that wireless transmission is achieved by broadcasting signals through the air, which has the potential for interfering with other parts of the network. Furthermore, the scarcity of wireless transmission resources implies that link activation and packet routing should be effected using simple distributed algorithms. We make three main contributions in the wireless setting. First, we determine graph classes under which simple, distributed, maximal weight schedulers achieve throughput optimality.(cont.) Second, we use this acquired knowledge of graph classes to develop combinatorial algorithms, based on matroids, for allocating channels to wireless links, such that each channel can achieve maximum throughput using simple distributed schedulers. Third, we determine new conditions under which distributed algorithms for joint link activation and routing achieve throughput optimality.by Andrew Brzezinski.Ph.D

Novel techniques in large scaleable ATM switches

Bibliography: p. 172-178.This dissertation explores the research area of large scale ATM switches. The requirements for an ATM switch are determined by overviewing the ATM network architecture. These requirements lead to the discussion of an abstract ATM switch which illustrates the components of an ATM switch that automatically scale with increasing switch size (the Input Modules and Output Modules) and those that do not (the Connection Admission Control and Switch Management systems as well as the Cell Switch Fabric). An architecture is suggested which may result in a scalable Switch Management and Connection Admission Control function. However, the main thrust of the dissertation is confined to the cell switch fabric. The fundamental mathematical limits of ATM switches and buffer placement is presented next emphasising the desirability of output buffering. This is followed by an overview of the possible routing strategies in a multi-stage interconnection network. A variety of space division switches are then considered which leads to a discussion of the hypercube fabric, (a novel switching technique). The hypercube fabric achieves good performance with an O(N.log₂N)²) scaling. The output module, resequencing, cell scheduling and output buffering technique is presented leading to a complete description of the proposed ATM switch. Various traffic models are used to quantify the switch's performance. These include a simple exponential inter-arrival time model, a locality of reference model and a self-similar, bursty, multiplexed Variable Bit Rate (VBR) model. FIFO queueing is simple to implement in an ATNI switch, however, more responsive queueing strategies can result in an improved performance. An associative memory is presented which allows the separate queues in the ATM switch to be effectively logically combined into a single FIFO queue. The associative memory is described in detail and its feasibility is shown by laying out the Integrated Circuit masks and performing an analogue simulation of the IC's performance is SPICE3. Although optimisations were required to the original design, the feasibility of the approach is shown with a 15Ƞs write time and a 160Ƞs read time for a 32 row, 8 priority bit, 10 routing bit version of the memory. This is achieved with 2µm technology, more advanced technologies may result in even better performance. The various traffic models and switch models are simulated in a number of runs. This shows the performance of the hypercube which outperforms a Clos network of equivalent technology and approaches the performance of an ideal reference fabric. The associative memory leverages a significant performance advantage in the hypercube network and a modest advantage in the Clos network. The performance of the switches is shown to degrade with increasing traffic density, increasing locality of reference, increasing variance in the cell rate and increasing burst length. Interestingly, the fabrics show no real degradation in response to increasing self similarity in the fabric. Lastly, the appendices present suggestions on how redundancy, reliability and multicasting can be achieved in the hypercube fabric. An overview of integrated circuits is provided. A brief description of commercial ATM switching products is given. Lastly, a road map to the simulation code is provided in the form of descriptions of the functionality found in all of the files within the source tree. This is intended to provide the starting ground for anyone wishing to modify or extend the simulation system developed for this thesis